Ultimate Dana Spicer 18 CJ2A / CJ3A / GPW Transfercase

Ok, this ‘case actually started life as a Dana 20 but eventually wound up in my possession and was converted to 18 spec with 2.46 gears and twin stick capability with the “pill” removed. I have been running it like this behind a T19 and a T18 that was hooked to a 134 L-head for years and more recently a Mercedes OM601 nonturbo diesel. This reliable old t case has dragged the old heep through thick and thin from Upper Helldoado in Moab to the Independence trail in Penrose. I was wishing for more reduction as 86-1 was not really enough for the really sticky situations as I found myself slipping the clutch to reduce my speed. Enter the neat piece of the day- a Wagoneer quadratrac low range unit. These worked similar to how a Warn overdrive worked but instead of a .75 overdrive it has a 2.57 UNDERdrive! Now these units share absolutely no common parts, shafts, splines, bolt patterns or anything else except that they both bolted to the back of their respective transfercases. The q-trac low range held up (pretty well) behind 360 and 401 AMC V8  engines in fullsize Wagoneers so Im figuring it will hold up to ~70 HP/ 100 LB-FT without struggling too much….. SO, I adapted one to the current t 18 d18 combo put it all together today and spent half the afternoon spinning the input shaft while watching the output barely turn. AHHH, the joys of ADD! 40 input turns to one output turn times the 5.43 9 inch ford rearend  gets me to  about 216 to one. That should do the trick!  The best part is that unlike all the other crawl box designs this one allows the same rear driveshaft to be used thus preserving what little it already did not have. This setup will probably test the durability of the 18 output shaft but time will tell…. at least I have spares.


4 responses to “Ultimate Dana Spicer 18 CJ2A / CJ3A / GPW Transfercase

  1. only flaw I see is – its not just 70hp / 110 ft-lb you’re working with, its multiplied by the 2.46 of the spicer lo-range, it is on-par with what you’d see if you had it behind a TH400 in high range

    • At the q trac input 695.2 lb-ft q trac output / 18 t/c input 1786.6 lb-ft 18 t/c output 4395.1 lb-ft . At the wheel 23,865 lb-ft.

  2. Hello Homer,
    I was wondering if you had any pictures of the adapter you made for the low range unit you’d be willing to share. I have a couple 18 cases and have access to a quadratrac. I sure would like to see what’s involved with putting the two together for my 1951 CJ3A.

    • I Do have some photos of this thing but it is a bunch more complicated than just

      a adapter unfortunately. Adapting it to a T90 would have its own set of complications but could probably be done…

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